Liquid fuse



Dem, 10, 1935a A, G. STEINMAYER LIQUID FUSE Filed OO.. 7, 195].

r a. Q c c c s a i Patented Dec. l0, 1935 UNITED STATES PATENT OFFICE LIQUID kFUSE Application Qctober 7, 1931, Serial No. 567,422

3 Claims. (C1. 20G- 117) This invention relates 'to liquid fuses.

Objects of this invention are to provide a novel form of liquid fuse Awhich will respond to overloads whether suddenly or gradually applied,

; which will quickly separate the two portions of the fuse link when fusing occurs, and which will quickly withdraw yone of Vthe fuse portions below the surface of an arc extinguishing liquid.

Further objects are to pro-vide a fuse of this general type which is so constructed that'the fuse link, although capable of being formed to respond to a small value of current, nevertheless is not subjected to undue or excessive mechanical strain, but which is so made that the upper g supporting member for the fuse may vconsist of a transversely extending 'memben such as a pin, which supports the fuse centrally of the container or tubular body portion, such supporting member or pin being of less length than the diameter of the opening provided by the blowing off of the diaphragm thereby allowing .the pin or supporting member to be freely discharged when the fuse blows.

Further objects are to provide Aa construction of liquid fuse in which a yielding closure member is provided which acts asa sealing gasket, which is readily ruptured and blown olf when the fuse blows, which also is expansible or yielding .to provide a gradually enlarging space above the liquid to take care of gases that are formed from the liquid when the fuse is gradually overloaded.

A further object is to provide a protecting cap for the yielding diaphragm which mechanically protects such diaphragm, but nevertheless is freely blown from the fuse when the fuse blows, such protecting cap being preferably held lightly in place by spring lingers.

Further objects are to Aprovide :a liquid fuse which is so constructed that when the closure disk or diaphragm blows off, an unobstructed, free opening is left through which .the supporting member for the fuse, .the upper portion of the fuse and the parts associated with the upper portion of the fuse may be freely expelled.

An embodiment of the invention is shown in the accompanying drawing, in Which:-

Figure l is a side elevation, partly in section, of the liquid fuse.

Figure 2 is a view of the upper portion of the liquid fuse, the section for such view being at right angles to that of Figure l.

Figure 3 is a sectional view on the line 3-3 of Figure l..

Referring to the drawing, it will be seen that the liquid fuse comprises a tubular or cylindrical container I, preferably of glass or other suitable insulating material, which is provided with a lower metal cap or contact member 2 and an upper metal sleeve or contact member 3 each secured to the glass tubular body portion I in a gas and liquid tight manner.

' The upper contact member, or sleeve 3, is 4externally threaded and receives the ring nut 4 which tightly clamps a gasket disk, or closure member 5, in place. The disk 5 is formed of a lo yielding and somewhat expansible material such as lead, aluminum, tinfoil, `or some other alloy which is soft and expansible.

This gasket disk 5 is compressible and, when clamped in place by the ring nut 4, forms a gas l5 seal, and is adapted to be ruptured, and the part closing the opening through the member 3 bodily blown away when the fuse blows, the inner edge of the ring nut 4 acting as a shear member. This provides an instantaneous relief for Ithe pressure gases and avoids placing excessive strain upon the glass body portion.

'I'he metal sleeve 3 is provided with diametrically opposed slots 6, see Figure 2, which are open at their upper ends and which are provided with abrupt shoulders at their lower ends. A transverse, fuse supporting pin I is loosely seated within the slots `and is of such a length that it may be freely blown out of the slots and through the ring nut 4 when the fuse blows. 30

It is preferable to provide a protecting outer plate 8 loosely positioned across the top of the ring nut 4 and protecting the sealing ydiaphragm or gasket 5 from mechanical ,damage as in handling. The 'plate 8 is provided with downwardly 35 extending vprongs 9 which terminate in inwardly rounded feet I3. The feet i0 snap beneath `the bevelled lower edge of the ring nut 4 and thus loosely hold the protecting plate 8 in place. The plate 8 does'not act as a seal or gasketbut merely 40 as a mechanical protector for the diaphragm 5. The plate f8 -is blown away when the diaphragm is ruptured and blown off.

The fuse link is a composite structure. It is composed of a pair of strips forming an upper portion II, and of a pair of strips forming the lower member I2. Either or both the upper and lower portions II and I2, respectively, may secure its double thickness by being folded longitudinally if desired.

The intermediate portion I3 of the fuse link is narrowed or reduced. This intermediate portion is formed by continuing only a single thickness of the lower member I2 upwardly between the two strips of the upper member I I, and soldering these parts together by a low melting point solder or alloy. The strips, forming the upper and lower members of the fuse link preferably have an appreciable resistance so that their reduced sections will generate sufficient heat, even with small overload, to melt the low melting point solder. The strips forming the fuse link may be composed of German silver, or other suitable material, to secure the characteristics desired such as the necessary mechanical strength and relectrical resistance, it of course being within the spirit of this invention to select the particular metal for the particular characteristics desired in any given case.

It will be seen that the heat is localized by reducing the intermediate section I3, and this localization of the heat may be further enhanced by surrounding the reduced intermediate section I3 with a cork I4, or other heat insulator, which is preferably split and held together by the banding wires I5.

The upper end of the fuse link is secured within a recess formed in the terminal 3, by means of a small screw I6 passing through the double thickness upper portion II. The lower end 'of the fuse link is secured by means of a screw I'i to iitting I8, such tting being apertured for the reception of an upwardly looped portion I9 of the spring 20. The fitting or member I8 has its lower portion tightly clamped around a flexible leader 2I.

The lower ends of both the spring 2e and the leader 2| are secured in any suitable manner to the lower contact 2.

The casing or tubular portion of the fuse is filled with an arc extinguishing liquid, such as carbon tetrachloride. Preferably the liquid extends to about the height indicated by the dotted line 22.

Any gas that may be generated by the heating of a small portion of the liquid will collect in the upper space above the liquid, but because of the yielding or extensible nature of the diaphragm 5, the pressure cannot rise much as the diaphragm will bow upwardly into the dotted shape indicated. Thus an additional protection is provided against bursting the glass tube I. When the fuse blows, the diaphragm is ruptured and its central portion blown from the fuse.

Due to the free and unobstructed opening through the top of the fuse, the upper portion of the fuse line, the cork I 4 and the pin 'I will be freely blown from the fuse and no choking of the fuse will occur. Thus, there is very little danger of bursting the tubular body portion.

The device can be readily re-fused and usedV over and over again.

It will be seen that a novel form of liquid fuse has been provided by this invention, and one that may be readily manufactured, handled, and used.

It will be seen that a liquid fuse has been provided which is of simple construction, which provides substantially instantaneous relief for the suddenly generated gases when the fuse blows, which provides a gradual relief or yielding diaphragm for any gases that may be gradually formed, and which is so made that both the diaphragm and the protecting cover are blown bodily from the device, the diaphragm being ruptured around its margins and the supporting pin or upper member for the fuse being blown through the opening afforded by the ruptured 10 diaphragm thereby providing a free and unob- Y structed upper opening.

Although the invention has been described in considerable detail, it is to be understood that such description is intended as illustrative and not limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:-

1. A liquid fuse comprising a tubular body portion adapted to contain an arc extinguishing liquid, an upper and a lower contact carried by said body portion, a pin carried by said upper Contact, a fuse link having its upper end secured to said upper contact and extending over said pin, and a spring secured to the lower end of said fuse link and to said lower contact and directly transmitting its tension to said fuse link.

2. A liquid fuse comprising a tubular body portion adapted to contain an arc extinguishing liquid, a lower contact and an annular upper contact carried by said body portion, a fuse link having its upper end secured to said upper contact at one side thereof, a pin extending transversely across and loosely carried by said upper contact and over which said fuse is passed, a spring secured to the lower contact and opera-V tively secured to the lower end of said fuse link, an expansible diaphragm closing said annular upper contact, and a ring nut screw threaded to said upper contact and clamping said diaphragm to said upper contact, said pin being of lesser length than the internal diameter of said ring nut, wherebyy said pin may freely pass through said ring nut when said fuse blows.

3. A liquid fuse comprising a tubular body portion adapted to contain an arc extinguishing liquid, a lower contact and an annular upper contact carried by said body portion, said annular contact having upwardly opening slots formed therein, a pin extending across said annular contact and loosely seated within said slots, a fuse link secured to said annular contact and extending over said pin,- a spring secured to said lower contact and operatively secured to the lower end of said fuse link, and rupturable means closing the upper portion of said annular contact whereby when said fuse blows, said last mentioned means is ruptured and said pin and the adjacent portions of said fuse are blown from said tubular body portion.

ALWIN G. STEINMAYER. 

